Magnetic Field Enhanced Electrocatalytic Oxygen Evolution by Ferrimagnetic Spinel Ferrites

Improving the electrocatalytic efficiency of the oxygen evolution reaction (OER) is critical for cost-effective hydrogen production. Among the various catalytic descriptors, the spin state and electronic structure of the catalyst have attracted considerable attention. The OER itself involves spin-sensitive reaction mechanisms, wherein singlet oxygen-containing reactants generate triplet oxygen molecules. Consequently, the spin state and spin alignment of the catalyst can reduce the OER overpotential. Furthermore, applying external magnetic fields to ferromagnetic catalysts enhances oxygen evolution kinetics by aligning the catalyst's spin with the spin-sensitive oxygen evolution pathway. The spinel ferrites have been synthesized with varying morphologies and investigated their electrocatalytic oxygen evolution performance under applied magnetic fields. CoFe 2 O 4 nanowires were initially prepared via electrospinning followed by calcination. At 1173 K, the treatment yielded intergrown nanoparticles that assembled into nanowire-like structures with exceptional magnetic characteristics: saturation magnetization of 88.9 emu/g and coercivity of 17,100 Oe at 2 K. Application of a 500 mT magnetic field substantially enhanced OER activity, producing a 100% magnetocurrent enhancement at 1.60 V vs. RHE. CoFe 2 O 4 and NiFe 2 O 4 nanoparticles have been synthesized by oxidative alkaline hydrolysis method. Magnetic characterization confirmed ferrimagnetic behaviour at room temperature, while structural and spectroscopic analyses verified the spinel phase lattice structure. Electrocatalytic studies in alkaline medium using nickel felt supports demonstrated excellent catalytic performance, achieving overpotentials of approximately 350 mV at 100 mA/cm². Upon application of a 500 mT external magnetic field, catalytic activities improved significantly, with reduced overpotential and enhanced current density at constant potential. The persistent effect of magnetic field on the OER electrocatalytic activity has been investigated. OER enhancement persists for several hours following magnetic field removal. The applied external magnetic field induces the spin polarization on the ferromagnetic catalyst, which plays the key role in the accelerating the spin sensitive oxygen evolution reactions. References van der Minne, Emma, Priscila Vensaus, Vadim Ratovskii, Seenivasan Hariharan, Jan Behrends, Cesare Franchini, Jonas Fransson et al. Advanced energy materials (2025), e03556. Wang, Zexuan, María F. Navarro Poupard, Ramsundar Rani Mohan, Loukya Boddapati, Jijun Zhang, Saeed Kamali, Chiara Biz et al. ACS nano 19, (2025), 29195-29206.